Thermostat.



J. S. HARLEY.

THERMOSTAT.

APPLICATION FILED MAY 22,1911.

Patented July 9, 1912.

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J OHN' S. HARLEY, OF MINNEAPOLIS, MINNESOTA,- ASSIGNOR, BY MESNE ASSIGNMENTS,

TO UNIVERSAL AUTOMATIC ELECTRIC SIGNALINGzCOMPANY, OF *LA CROSSE, WIS- CONS IN, A CORPORATION OF WISCONSIN.

THERMOSTAT'. i

Specification of Letters latent.

Patented July 9, 1912.

To all whom it may concern:

Be it known that I, JOHN S.'I-IARLEY, a citizen of theUnited States, residing at Minneapolis, in the county of Hennepin and State of Minnesota, have invented certain new and useful Improvements in Thermostat-s, of which the following is a specification.

My invention relates to an improved thermostat which when placed in a circuit will operate normally to close said circuit, but which in case of fire will respond to a comparatively low degree of heat to break the circuit whereby an alarm may be signaled through mechanism set in operation by the breaking of said circuit.

In fire alarm systems it is desirable that the detection means shall be such that not only will the presence of fire be unfailingly signaled but also other abnormal conditions. which would render the system inoperative To obtain a system involvinga closed circuit, such for example as that described in my application Serial Number 628,873, dated May 22, 1911, for fire. alarm systems, is essential,

/ the operation of the alarm signaling'de'vice following the breaking of such closed circuit. To provide meansfor breaking such a circuit very promptly upon the occurrenceof a fire I have invented the thermostat herein described. The principles upon which this thermostat operates are fundamentally the provision of a member in the circuit normally closing said circuit, part of said member forming part of said circuit consisting of a mobile conducting liquid held in position by somesubstance fusible at a comparatively low temperature-so that when'thefusible substance is melted by the first heat of the fire the conducting liquid will flow from the thermostat thereby breaking the circuit.

The full objects and advantages of my invention will be given inconnection with the detailed description thereof and are particularly pointed out in the claims.

In the drawings illustrating one form of my invention,-Figure 1 is a sectional view of my improved thermostat. Figs. 2 and 3 side and elevation views, respectively, of a form of the thermostat attached to .a wall.

Figs. 4 and 5 show another form of connect- I ing means for placing the thermostat-in position so that the opening will certainly be turned down. Figs. 6 and 7 are detail views Fig. 8 is aof the same securing means. section on line 88 of Fig. 1. Fig. 9 is a side sectional view of the contact spring for securing the thermostat in position.

My thermostat comprises a tubular body portion 10 of fiber, rubber, glass or other,

non-conducting material having extendingwithin the same at each end thereof metal pins 11, 12, each pin being provided with a curved head 13 and extending within the tubular member 10 to a-distance less than one-half the length thereof so that there will be an intervening space 14 between the ends ofthe pins 11' and 12. The space 14 will be filled with mercury or any other mobile conducting liquid which by contact with the ends of the pins 11 and 12 will provide means for closing any circuit in which the thermostat may be used. Upon,

one side of the body portion 10 opposite the cavity 14 an opening '15 is formed which may be of any desired shape, the circular or slightly oval shown being found very satisfactory. I have also found it to be effective for the purpose intended to bevel the walls of said opening inwardly as shown at 16. Before assembling the pins 11 .and 12 and the conducting liquid within the tube.v

10 the inner walls thereof are preferably waxed or covered with a 'thin layer .of

grease, has been, placed within the cavity .14 the openin 15 from said cavity is sealed with a layer of readily at 17 For this purpose nary tallow to be very'satisfactory, but-the use. of other melt at the desired temperature to release the mercury or liquid from the cavity is contemplated by me and falls within the.

scope of my invention.

My thermostat may be formed with both" heads 13 semi-spherical, as shown in Fig. 2,

- and may be held within the circuit'by spring fusible material, as shown' I have found ordi-' fusible substances .which will and when the mercury or other liquid 7 in position and provide the contacts for completing the circuit. I do not, however, limit myself to the use of a thermostat with a bridge, since it is practicable and falls.

within the scope of my invention to connect my thermostat directly to the wires of a circuit without the use of any bridge, and since the tubular portion 10 of my thermostat is non-conducting I may secure said thermostat directly to the walls or ceiling of a room and the wires directly to the ends of the thermostat. It is, however, essential to the operation of my device that whereever the thermostat may be placed the opening 15 shall be faced directly downwardly. To render it impossible to place the thermostat in any other position, the attaching means shown in Figs. 1 and 4 to 7 inclusive, may be used. In this form, in place of the spring metal contact strip 19, a longitudinally positioned strip 22 is used having a bifurcated upper end 23 provided with a side slot 24. Extending from one of the heads 13 is a flat member 25 having a rightangled bend 26 adapted to seat within the slot 24 when the thermostat is placed in the circuit. As the slot 24: is at one side only the position of the bend 26 is such as to make it impossible to assemble the thermostat in the bridge inany position excepting with the. opening 15 turned down. The relative position of the bend 26 with respect to the opening will, of course, have to be varied to adapt the thermostats to be attached either to the walls or ceiling.

In use my improved thermostat being positioned in a circuit with the opening 15 turned down will maintain the circuit closed under normal conditions. Should, however, a fire occur at any point near where the thermostat is located, the first rise in temperature resulting therefrom will melt the fusible seal 17 whereupon the mercury or other conducting liquid within the cavity 14 will run out through the opening 15 thus breaking the circuit and causing the signaling means to operate. By reason of the fact that the inner wall of the tubular member 10 is waxed or greased all of such liquid conductor will'instantly leave the cavity 1 1 so that the circuit will unfailingly be broken.

My improved thermostat can be made very cheaply and assembled in a circuit with the greatest ease so that a large number of such thermostats may economically be placed in each room orv department of the building protected by the fire alarm signaling system. The thermostats cannot get out of repair and, although responsive with extreme rapidity to a rise in temperature above the fusing point of the wax or grease seal 17, are not sensitive in any other particular and therefore are peculiarly free from becoming inoperative or operating improperly on account of conditions other than those relating to temperature.

I claim:

1. A thermostat comprising a tube of nonconducting material, conducting members entering the tube at each end thereof and filling the said ube except for a space between the separated ends of said conductors, said cavity being filled with mercury and opening through the wall of said tube, a fusible seal closing said opening, a bridge for receiving said thermostat comprising a slotted cont-act, and an extension plate on at least one of said conduct-ing members having a member for engaging said slot whereby the thermostat will be positioned in the circuit with the opening facing downward. 2. A thermostat comprising an openended smooth-walled tube of non-conducting material having a centrally positioned opening through the wall thereof, said opening being round or oval in form and having inwardly beveled sides, the inner walls of said tube being coated with grease or wax, conducting members extending within the tube at each end thereof and filling the same to a point near the edges of said opening so as to leave a cavity into which the opening extends and of substantially the same length as the longer diameter of said opening, said cavity being filled with mercury, and a seal of readily fusible material normally held in position to close said opening and retain the mercury within the cavity by the beveled sides of said opening.

In testimony whereof I afiixmy signature in presence of two witnesses.

JOHN S. HARLEY.

Witnesses:

F. A. Wnmnnr, H. A. Bowman. 

